As big as it is, MocoSpace still has plenty of room to grow: the company estimates that as many as 30 to 40 million feature-phone owners are under age 30 and have access to data plans. In my conversation with Hall and Siegel, an edited version of which appears below, I asked about how the company optimizes social-networking services for feature phones, how the mobile advertising scene is evolving, and what sorts of new features might be coming down the road. (Don’t be too surprised if MocoSpace eventually gives in to fashion and builds a dedicated iPhone app—as the Apple device becomes more ubiquitous, Hall and Siegel say they want to keep serving the core audience of mobile-addicted young people.)